Solution to the problem of minimum distance detection of various objects in shallow water depth

Abstract

Object and purpose of research. The object of research is arrangement of various items on the bottom of water bodies. The purpose of research is achieving maximum invisibility for such items. Anticipated search or accidental detection of bottom objects can be carried out by the bathymetric method, i.e. assessment of water column over such objects. Materials and methods. It is expected that low flying UAVs (unmanned aerial vehicles) equipped with bathymetric laser emitter are used for detection of underwater objects. With consideration of some simplifications, optimization is carried out for the operation of bathymetric laser detector of objects located on the sea bed. The task of detecting an underwater object is considered to be solved when the difference between the signals reflected from the sea bed and underwater object is reliably recorded. Minimum external detectability is achieved at minimum of the said difference. Main results. An objective functional is obtained to characterize the total signal from multiple underwater objects. As a result of performed optimization, the condition is determined at which the minimum of the objective functional is achieved. According to the obtained result, the total signal reflected from an underwater object reaches its minimum if the height of underwater objects and their reflection coefficient vary paraphase, i.e. the growth of one is accompanied with the reduction of the other. Conclusion. A method for minimum detectability of objects stacked on the sea bed is suggested and validated. Practical procedures of storing various objects on the sea bed are defined, which ensures their invisibility for the bathymetric laser detector onboard the low-flying UAV.